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  • 1.
    Adhikari, Arindam
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pani, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Deidinaitei, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Electrochemical behavior and anticorrosion properties of modified polyaniline dispersed in polyvinylacetate coating on carbon steel2008In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, no 12, 4239-4247 p.Article in journal (Refereed)
    Abstract [en]

    Conducting polyaniline (Pani) was prepared in the presence of methane sulfonic acid (MeSA) as dopant by chemical oxidative polymerization. The Pani-MeSA polymer was characterized by FT-IR, UV-vis, X-ray diffraction (XRD) and impedance spectroscopy. The polyrner was dispersed in polyvinylacetate and coated oil carbon steel samples by a dipping method. The electrochemical behavior and anticorrosion properties of the coating, oil carbon steel in 3% NaCl were investigated using Open-circuit Potential (OCP) versus time of exposure, and electrochemical techniques including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and cyclic voltammetry (CV). During initial exposure, the OCP dropped about 0.35 V and the interfacial resistance increased several times, indicating I certain reduction of the polymer and oxidation of the steel surface. Later the OCP shifted to the noble direction and remained at a stable value during the exposure up to 60 days. The EIS monitoring also revealed the initial change and later stabilization of the coating. The stable high OCP and low coating impedance Suggest that the conducting polymer maintains its oxidative state and provides corrosion protection for carbon steel through out the investigated period. The polarization curves and CV show that the conducting polymer coating induces a passive-like behavior and greatly reduces the corrosion of carbon steel.

  • 2.
    Adhikari, Arindam
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Radhakrishnan, S.
    Patil, Rahul
    Influence of dopant ions on properties of conducting polypyrrole and its electrocatalytic activity towards methanol oxidation2009In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 159, no 15-16, 1682-1688 p.Article in journal (Refereed)
    Abstract [en]

    The polypyrrole (PPy) films were deposited on vacuum metallized substrates by electro-oxidation of pyrrole monomer. These electrodes were then modified with a range of metal halides having different electronegativities. The modified polypyrrole electrodes were employed to investigate electrocatalytic activity towards methanol electrochemical oxidation by means of cyclic voltammetry in 0.1 M HClO4 as supporting electrolyte. It was found that the electronegativity of the dopant ion incorporated in the PPy film governs the electrocatalytic activity towards methanol oxidation. Among different dopant anions used in the present work, the PPy doped with zirconium chloride gave the highest anodic current of 10 mA cm(-2) at the oxidation potential of methanol. Electrical property and the charge created due to doping in the polymers were measured using X-ray photoelectron spectroscopy (XPS) and Electron spin resonance spectroscopy (ESR). Electrocatalytic activity of the modified electrodes was correlated with various factors obtained from different polymer characterization experiments. The results were explained on the basis of the charge-transfer efficiency at the electrode I electrolyte interface, which was associated with the acceptor state created by the dopant in the semi-conducting polymer.

  • 3.
    An, Junxue
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Biomolecular association – biolubrication perspective: Association between hyaluronan and phospholipids2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Dipalmitoylphosphatidylcholine (DPPC) vesicles were prepared by sonication and their size in sodium chloride solutions ([NaCl] = 0.116 M) containing different amount of calcium ions (0, 1, 2, 5, 10 mM) were studied by Dynamic Light Scattering (DLS). The time dependence of the particle size in various solutions was also tested. The data showed that the hydrodynamic diameter of DPPC vesicles was not affected by the Ca2+ concentration; however, the stability of DPPC vesicles was improved with the presence of Ca2+. Besides, when the temperature was above the phase transition temperature (41.5°C), the DPPC vesicles in dispersions with more than 2 mM CaCl2 remained stable for at least 2 weeks. Zeta potential of vesicles in aqueous solutions was tested by Zetasizer. The result showed that the stability of DPPC vesicles increased with increasing Ca2+ concentration with the evidence of increasing zeta potential due to the binding of Ca2+ onto vesicle bilayers. The association between zwitterionic DPPC vesicles and anionic polyelectrolyte hyaluronan (HA) was also studied by testing the hydrodynamic diameter and electrophoretic mobility change after the addition of HA. DLS results showed that the hydrodynamic diameter of DPPC vesicles increased in the presence of HA. In addition, after several days’ incubation at 55°C precipitation appeared in the DPPC-HA mixture solution. Furthermore, electrophoretic mobility of DPPC vesicles decreased after the addition of polyelectrolyte. The combined results demonstrated that the association between DPPC and HA occurred.

  • 4.
    Arvidsson, Martin
    et al.
    Department of Psychology, Stockholm University, Sweden.
    Berglund, Birgitta
    Department of Psychology, Stockholm University, Sweden.
    Skedung, Lisa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Aikala, Maiju
    Oy Keskuslaboratorio - Centrallaboratorium Ab (KCL), Espoo, Finland.
    Danerlöv, Katrin
    Institute for Surface Chemistry (YTK), Stockholm, Sweden.
    Kettle, John
    Oy Keskuslaboratorio - Centrallaboratorium Ab (KCL), Espoo, Finland.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Multidimensional psychophysics: surface feel of printing paper as a function of physical propertiesManuscript (preprint) (Other academic)
  • 5. Attard, Phil
    et al.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231). Ytkemiska Institutet, Sweden.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231). Ytkemiska Institutet, Sweden.
    Thermal calibration of photodiode sensitivity for atomic force microscopy2006In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 77, no 11Article in journal (Refereed)
    Abstract [en]

    The photodiode sensitivity in the atomic force microscope is calibrated by relating the voltage noise to the thermal fluctuations of the cantilever angle. The method accounts for the ratio of the thermal fluctuations measured in the fundamental vibration mode to the total, and also for the tilt and extended tip of the cantilever. The method is noncontact and is suitable for soft or deformable surfaces where the constant compliance method cannot be used. For hard surfaces, the method can also be used to calibrate the cantilever spring constant.

  • 6. Attard, Phil
    et al.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Stiernstedt, johanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Measurement of friction coefficients with the atomic force microscope2007In: PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY / [ed] Meyer, E; Hegner, M; Gerber, C; Guntherodt, HJ, Bristol: Iop Publishing Ltd , 2007Conference paper (Refereed)
    Abstract [en]

    A new axial method for measuring the friction coefficient with the atomic force microscope is given. This axial method requires no calibration steps and is performed simultaneously with a normal force measurement by measuring the difference between the constant compliance slopes of the extend and retract force curves. The algorithm can be applied retrospectively to extract the friction coefficient from preexisting force measurements. Results are in quantitative agreement with the more established lateral method. The method can be used for both tipped cantilevers and for attached spherical probes.

  • 7.
    Bastardo Zambrano, Luis Alejandro
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Self assembly of surfactants and polyelectrolytes in solution and at interfaces2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis focuses on the study of the interactions between polyelectrolytes and surfactants in aqueous solutions and at interfaces, as well as on the structural changes these molecules undergo due to that interaction. Small–angle neutron scattering, dynamic, and static light scattering were the main techniques used to investigate the interactions in bulk. The first type of polymer studied was a negatively charge glycoprotein (mucin); its interactions with ionic sodium alkyl sulfate surfactants and nonionic surfactants were determined. This system is of great relevance for several applications such as oral care and pharmaceutical products, since mucin is the main component of the mucus layer that protects the epithelial surfaces (e.g. oral tissues). Sodium dodecyl sulfate (SDS) on the other hand, has been used as foaming agent in tooth pastes for a very long time. In this work it is seen how SDS is very effective in dissolving the large aggregates mucin forms in solution, as well as in removing preadsorbed mucin layers from different surfaces. On the other hand, the nonionic surfactant n-dodecyl β-D-maltopyranoside (C12-mal), does not affect significantly the mucin aggregates in solution, neither does it remove mucin effectively from a negatively charge hydrophilic surface (silica). It can be suggested that nonionic surfactants (like the sugar–based C12-mal) could be used to obtain milder oral care products. The second type of systems consisted of positively charged polyelectrolytes and a negatively charged surfactant (SDS). These systems are relevant to a wide variety of applications ranging from mining and cleaning to gene delivery therapy. It was found that the interactions of these polyelectrolytes with SDS depend strongly on the polyelectrolyte structure, charge density and the solvent composition (pH, ionic strength, and so on). Large solvent isotopic effects were found in the interaction of polyethylene imine (PEI) and SDS, as well as on the interactions of this anionic surfactant and the sugar–based n-decyl β-D-glucopyranoside (C10G1). These surfactants mixtures formed similar structures in solutions to the ones formed by some of the polyelectrolytes studied, i.e. ellipsoidal micelles at low electrolyte concentration and stiff rods, at high electrolyte and SDS concentrations.

  • 8.
    Bastardo Zambrano, Luis Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Garamus, V. M.
    GKSS Research Centre, Geesthacht.
    Bergström, Lars Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    The structures of complexes between polyethylene imine and sodium dodecyl sulfate in D2O: a scattering study2005In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 1, 167-174 p.Article in journal (Refereed)
    Abstract [en]

    The association between a highly branched polyelectrolyte with ionizable groups, polyethylene imine (PEI), and an anionic surfactant, sodium dodecyl sulfate (SDS), has been investigated at two pH values, using small-angle neutron and light scattering. The scattering data allow us to obtain a detailed picture of the association structures formed. Small-angle neutron scattering (SANS) measurements in solutions containing highly charged PEI at low pH and low SDS concentrations indicate the presence of disklike aggregates. The aggregates change to a more complex three-dimensional structure with increasing surfactant concentration. One pronounced feature in the scattering curves is the presence of a Bragg-like peak at high q-values observed at a surfactant concentration of 4.2 mM and above. This scattering feature is attributed to the formation of a common well-ordered PEI/SDS structure, in analogue to what has been reported for other polyelectrolyte-surfactant systems. Precipitation occurred at the charge neutralization point, and X-ray diffraction measurements on the precipitate confirmed the existence of an ordered structure within the PEI/SDS aggregates, which was identified as a lamellar internal organization. Polyethylene imine has a low charge density in alkaline solutions. At pH 10.1 and under conditions where the surfactant was contrast matched, the SANS scattering curves showed only small changes with increasing surfactant concentration. This suggests that the polymer acts as a template onto which the surfactant molecules aggregate. Data from both static light scattering and SANS recorded under conditions where SDS and to a lower degree PEI contribute to the scattering were found to be consistent with a structure of stacked elliptic bilayers. These structures increased in size and became more compact as the surfactant concentration was increased up to the charge neutralization point.

  • 9.
    Bastardo Zambrano, Luis Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Iruthayaraj, Joseph
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Lundin, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Dédinaité, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Vareikis, Aušvydas
    Department of Polymer Chemistry, Vilnius University.
    Makuška, Ričardas
    Department of Polymer Chemistry, Vilnius University.
    van der Wal, Albert
    Lever Faberage Europe Global Technology Centre, Unilever R and D.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Garamus, Vasil M.
    GKSS Research Centre.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 312, no 1, 21-33 p.Article in journal (Refereed)
    Abstract [en]

    A low charge density polyelectrolyte with a high graft density of 45 units long poly(ethylene oxide) side-chains has been synthesized. In this comb polymer, denoted PEO(45)MEMA:METAC-2, 2 mol% of the repeating methacrylate units in the polymer backbone carry a permanent positive charge and the remaining 98 mol% a 45 unit long PEO side-chain. Here we describe the solution conformation of this polymer and its association with an anionic surfactant, sodium dodecylsulfate, SDS. It will be shown that the polymer can be viewed as a stiff rod with a cross-section radius of gyration of 29 A. The cross section of the rod contracts with increasing temperature due to decreased solvency of the PEO side-chains. The anionic surfactant associates to a significant degree with PE045MEMA:METAC-2 to form soluble complexes at all stoichiometries. A cooperative association is observed as the free SDS concentration approaches 7 mM. At saturation the number of SDS molecules associated with the polymer amounts to 10 for each PEO side-chain. Two distinct populations of associated surfactants are observed, one is suggested to be molecularly distributed over the comb polymer and the other constitutes small micellar-like structures at the periphery of the aggregate. These conclusions are reached based on results from small-angle neutron scattering, static light scattering, NMR, and surface tension measurements.

  • 10.
    Bastardo Zambrano, Luis Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Mészaros, R.
    Department of Colloid Chemistry, Eötvös Loránd University, Budapest.
    Varga, I.
    Department of Colloid Chemistry, Eötvös Loránd University, Budapest.
    Gilanyi, T.
    Department of Colloid Chemistry, Eötvös Loránd University, Budapest.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Deuterium isotope effects on the interaction between hyperbranched polyethylene imine and an anionic surfactant2005In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 33, 16196-16202 p.Article in journal (Refereed)
    Abstract [en]

    Solvent isotope effects on the interaction between the hyperbranched cationic polyelectrolyte, polyethylene imine (PEI), and the anionic surfactant sodium dodecyl sulfate (SDS) were investigated using potentiometric titration and eletrophoretic mobility measurements. In the basic pH range, a significantly higher fraction of the amine groups was found to be protonated when the PEI was dissolved in D2O compared to H2O at the same pH/pD. The difference in polymer charge in the two solvents decreases gradually with decreasing pH, and it completely diminishes at around pH = 4. Electrophoretic mobility measurements of PEI/SDS complexes at different pH values correlated very well with these observations. At pH/pD approximate to 9 a much higher mobility of the PEI/SDS complexes was found in D2O than in H2O at low surfactant concentrations, and the charge neutralization point shifted to a considerably larger surfactant concentration in heavy water. These results can be explained by the significantly higher charge density of the PEI in D2O compared to H2O. However, at the natural pH/pD as well as at pH = 4 and pD = 4 conditions the PEI molecules have roughly equal charge densities, which result in very similar charged characteristics (mobilities) of the PEI/SDS complexes as well as the same charge neutralization SDS concentration. It can be concluded that extreme care must be taken in the general analysis of those experiments in which weak polyelectrolyte/surfactant aggregates are investigated in heavy water, and then these observations are correlated with structures of the same system in water.

  • 11. Baverback, Petra
    et al.
    Oliveira, Cristiano L. P.
    Garamus, Vasil M.
    Varga, Imre
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pedersen, Jan Skov
    Structural Properties of beta-Dodecylmaltoside and C12E6 Mixed Micelles2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 13, 7296-7303 p.Article in journal (Refereed)
    Abstract [en]

    Mixed micelles formed in aqueous solutions of nonionic surfactants n-dodecyl-hexaethylene-glycol (C12E6) and n-dodecyl-beta-D-maltoside (C(12)G(2)) have been studied using small-angle neutron and X-ray scattering (SANS and SAXS) and static light scattering (SLS). Apparent micelle molar masses obtained with SLS were analyzed with a model taking into account both micelle growth and interference effects. The analysis shows that pure C(12)G(2) forms small globular micelles whereas C12E6 and the mixtures form elongated micelles of much higher molar mass. The elongated micelles grow with increased concentration according to mean-field theory, and the masses are larger for increasing amounts of C12E6. To describe the SANS and SAXS data for C12E6 and the mixtures, it: was necessary to employ a model with coexisting spherical and spherocylindrical micelles. The SANS and SAXS data were fitted simultaneously using this model with core-shell particles and molecular constraints. All mixtures, as well as pure C12E6, can be described by this model, demonstrating the coexistence of spherical and cylindrical micelles. The spherical micelles are the same size in all samples, whereas the cylindrical micelles grow in length with the fraction of C12E6 in the samples, as well as with concentration, in agreement with the SLS analysis. The mass fraction of surfactant in cylindrical aggregates also increases with the fraction of C12E6 and with overall concentration. The analysis of the SAXS and SANS data for pure C(12)G(2) shows that the micelles are disk-shaped. The presence of elongated micelles in pure C12E6 and in the mixtures demonstrates that the behavior of the mixtures is dominated by C12E6.

  • 12.
    Bergenstråhle, Malin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Nordgren, Niklas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Force Pulling of Single Cellulose Chains at the Crystalline Cellulose-Liquid Interface: A Molecular Dynamics Study2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 8, 4635-4642 p.Article in journal (Refereed)
    Abstract [en]

    Pulling single cellulose molecules from a crystalline cellulose surface has been modeled by molecular dynamics (MD) simulations of the experimental procedure used in atomic force microscopy (AFM). Specifically, the aim of the study was to investigate cellulose interactions at desorption. Simulations were performed in both water and the organic solvent cyclohexane. Moreover, the effects of initial octamer conformation and orientation with respect to the surface chains were studied. A strong effect from the solvent was observed. In cyclohexane, normal forces of 200-500 pN and energies of 43.5 +/- 6.0 kJ/mol glucose unit were required to pull off the octamer. The normal forces in water were substantially lower, around 58 pN, and the energies were 18.2 +/- 3.6 kJ/mol glucose unit. In addition, the lateral components of the pull-off force were shown to provide information on initial conformation and orientation. Hydrogen bonds between the octamer and surface were analyzed and found to be an important factor in the pull-off behavior. Altogether, it was shown that MD provides detailed information on the desorption processes that may be useful for the interpretation of AFM experiments.

  • 13.
    Bergström, L.
    et al.
    YKI, Institute for Surface Chemistry.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Probing polymeric stabilization in nonaqueous media by direct measurements2000In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 83, no 1, 217-219 p.Article in journal (Refereed)
    Abstract [en]

    The steric repulsion induced by adsorbed layers of the commercial dispersant Hypermer KD3 has been probed by direct measurements in decalin. The forces are long range (commencing at 30-40 nm) and repulsive, and the distance dependence can be modeled with a simple scaling theory expression valid for polymer brushes. We obtain layer thicknesses of similar to 9-15 nm for the compressed layers, depending on KD3 concentration, whereas the undisturbed layers have a thickness of similar to 23-24 nm, independent of polymer concentration. Comparison of the measured interaction lengths with previous layer thickness estimates based on rheological studies shows that the polymer layers are compressed in dense suspensions.

  • 14.
    Bergström, L. M.
    et al.
    Department of Pharmacy, Pharmaceutical Physical Chemistry, Uppsala University.
    Bastardo Zambrano, Luis Alejandro
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Garamus, V. M.
    GKSS Research Centre, Geesthacht.
    A small-angle neutron and static light scattering study of micelles formed in aqueous mixtures of a nonionic alkylglucoside and an anionic surfactant2005In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 25, 12387-12393 p.Article in journal (Refereed)
    Abstract [en]

    The size and shape of micelles formed in aqueous mixtures of the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic sugar-based surfactant n-decyl beta-D-glucopyranoside (C(10)G) at different concentrations of added salt have been investigated with small-angle neutron and static light scattering. Rather small prolate ellipsoidal micelles form in the absence of added salt and at [NaCl] = 10 mM in D2O. The micelles grow considerably in length to large rods as the electrolyte concentration is raised to [NaCl] = 0.1 M. In excess of nonionic surfactant ([SDS]/[C(10)G] = 1:3) at [NaCl] = 0.1 M in D2O, several thousands of Angstroms long wormlike micelles are observed. Most interestingly, a conspicuously large isotope solvent effect was observed from static light scattering data according to which micelles formed at [SDS]/[C(10)G] = 1:3 and [NaCl] = 0.1 M in H2O are at least five times smaller than micelles formed in the corresponding samples in D2O.

  • 15.
    Bergström, Lars Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Bending Elasticity of Nonionic Surfactant Layers2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 4, 1949-1960 p.Article in journal (Refereed)
    Abstract [en]

    A novel approach to evaluate the bending elasticity of monolayers formed by nonionic surfactants with a rigid head group is introduced by means of considering head group repulsion as derived from the free energy of mixing rigid hydrophilic head groups with surrounding solvent molecules as well as contributions related to the hydrophobic tails. Explicit expressions for the spontaneous curvature (H-0), bending rigidity (k(c)) and saddle-splay constant ((k) over bar (c)) have been derived for the constraint of constant chemical potential of free surfactant (thermodynamically open layers) as well as the constraint of constant aggregation number (thermodynamically closed layers). Most interestingly, it is demonstrated that k(c) for thermodynamically open layers formed by a nonionic surfactant with rigid tail and head group always must be zero. However, k(c) for surfactants with a flexible tail as a function of the head group-to-tail volume ratio is found to go through a maximum at some large, positive value of k(c) and H-0 approximate to 0. Eventually, k(c) falls below zero as the head group volume increases above a certain value. Hence, we may conclude that nonionic surfactants with a rigid head group may form thermodynamically stable fluid layers or aggregates only insofar the hydrophobic part is flexible with respect to chain conformational. degrees of freedom and the head group is not too voluminous. It is found that the head group repulsion contribution to k(c)H(0) is always positive whereas the corresponding contribution to (k) over bar

  • 16.
    Bergström, Lars Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Thermodynamics and bending energetics of toruslike micelles2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 327, no 1, 191-197 p.Article in journal (Refereed)
    Abstract [en]

    The self-assembly of surfactants forming toruslike or toroidal micelles has been investigated from a theoretical point of view, in particular the structural behaviour and stability of tori in terms of the three bending elasticity constants spontaneous curvature (H-0), bending rigidity (k(c)) and saddle-splay constant (kc). It is demonstrated that the size of toruslike micelles increases with an increasing bending rigidity, but is independent of both spontaneous Curvature and saddle-splay constant. Similar to conventional micelles, toruslike micelles are found to be stable over bilayers as the spontaneous curvature times the surfactant layer thickness exceeds 1/4. Moreover, it is shown that toruslike micelles, in general, are favoured at the expense of long spherocylindrical micelles as a result of elimination of the unfavourable end-caps. However, conventional micelles that are able to grow with respect to both width and length (tablets) may be stable over tori as well as spheres in much wider regimes of different bending elasticity constants. As a result, toruslike micelles are predicted to be stable over conventional micelles, including rods, at large values of the effective bending constant k(eff) equivalent to 2k(c) +(k) over bar (c), i.e. in the same region where infinite cylinders are expected to be observed. This result is consistent with the fact that toruslike micelles have usually been observed to coexist with large networks of branched cylinders.

  • 17.
    Bergström, Lars Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Bramer, Tobias
    Synergistic effects in mixtures of oppositely charged surfactants as calculated from the Poisson-Boltzmann theory: A comparison between theoretical predictions and experiments2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 322, no 2, 589-595 p.Article in journal (Refereed)
    Abstract [en]

    Critical micelle concentrations in mixtures of an anionic surfactant and a cationic amphiphilic drug have been investigated using a model-independent procedure to quantify observed synergistic effects. Experimental results were compared with a theory based on the Poisson-Boltzmann mean field approximation of a charged interface with a diffuse layer of counterions. Explicit expressions for the activity coefficients from which the critical micelle concentration can be calculated and quantitatively predicted have been derived and excellent agreement between experimental data and theory was obtained. As a result, we demonstrate that it is possible to rationalize and predict the magnitude of synergism in mixtures of oppositely charged surfactants in the presence of added salt.

  • 18.
    Bijelic, Goran
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Interfacial properties of bottle-brush polyelectrolytes and lipids2010Licentiate thesis, comprehensive summary (Other academic)
  • 19.
    Bijelic, Goran
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Hermanowska, Malgorzata
    Klösgen, Beate
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Physicochemical properties of 1-palmitoyl-2-oleoyl-sn- glycero-3-phosphocholine (POPC) monolayers - influence of charge addition and temperatureManuscript (preprint) (Other (popular science, discussion, etc.))
  • 20.
    Bijelic, Goran
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Shovsky, Alexander
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Varga, Imre
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Makuska, Ricardas
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Adsorption characteristics of brush polyelectrolytes on silicon oxynitride revealed by dual polarisation interferometry2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 348, 189-197 p.Article in journal (Refereed)
    Abstract [en]

    Adsorption properties of bottle-brush polyelectrolytes have been investigated using dual polarization interferometry (DPI), which provides real time monitoring of adsorbed layer thickness and refractive index. The adsorption on silicon oxynitride was carried out from aqueous solution with no added inorganic salt, and the adsorbed polyelectrolyte layer was subsequently rinsed with NaCl solutions of increasing concentration. The bottle-brush polyelectrolytes investigated in this study have different ratios of permanent cationic charged segments and uncharged PEO side chains. Both the cationic groups and the PEO side chains have affinity for silica-like surfaces, and thus contribute to the adsorption process that becomes rather complex. Adsorption properties in water, responses to changes in ionic strength of the surrounding medium, adsorption kinetics and the layer structure are all strongly dependent on the ratio between backbone charges and side chains. The results are interpreted in terms of competitive adsorption of segments with different chemical nature. The adsorption kinetics is relatively fast, taking only tens to hundreds of seconds when adsorbed from dilute 100 ppm solutions. The DPI technique was found to be suitable for studying such rapid adsorption processes, including determination of the initial adsorption kinetics. We expect that the effects observed in this study are of general importance for synthetic and biological polymers carrying segments of different nature.

  • 21.
    Blomberg, Eva
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Konradsson, Peter
    Department of Physics, Chemistry and Biology, Linköping University.
    Liedberg, Bo
    Department of Physics, Chemistry and Biology, Linköping University.
    Globotriose- and oligo(ethylene glycol)-terminated self-assembled monolayers: Surface forces, wetting, and surfactant adsorption2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 24, 10038-10046 p.Article in journal (Refereed)
    Abstract [en]

    A set of oligo( ethylene glycol)-terminated and globotriose-terminated self-assembled monolayers (SAMs) has been prepared on gold substrates. Such model surfaces are well defined and have good stability due to the strong binding of thiols and disulfides to the gold substrate. They are thus very suitable for addressing questions related to effects of surface composition on wetting properties, surface interactions, and surfactant adsorption. These issues are addressed in this report. Accurate wetting tension measurements have been performed as a function of temperature using the Wilhelmy plate technique. The results show that the nonpolar character of oligo( ethylene glycol)-terminated SAMs increases slightly but significantly with temperature in the range 20-55 degrees C. On the other hand, globotriose-terminated SAMs are fully wetted by water at room temperature. Surface forces measurements have been performed and demonstrated that the interactions between oligo( ethylene glycol)-terminated SAMs are purely repulsive and similar to those determined between adsorbed surfactant layers with the same terminal headgroup. On the other hand, the interactions between globotriose-terminated SAMs include a short-range attractive force component that is strongly affected by the packing density in the layer. In some cases it is found that the attractive force component increases with contact time. Both these observations are rationalized by an orientation- and conformation-dependent interaction between globotriose headgroups, and it is suggested that hydrogen-bond formation, directly or via bridging water molecules, is the molecular origin of these effects.

  • 22.
    Blomberg, Eva
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Kumpulainen, Atte
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    David, C.
    Laboratoire de Recherche sur les Polymères, CNRS, Thiais, France.
    Amiel, C.
    Laboratoire de Recherche sur les Polymères, CNRS, Thiais, France.
    Polymer bilayer formation due to specific interactions between beta-cyclodextrin and adamantane: A surface force study2004In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, no 24, 10449-10454 p.Article in journal (Refereed)
    Abstract [en]

    The purposes of this study are to utilize the interactions between an adamantane end-capped poly(ethylene oxide) (PEO) and a cationic polymer of beta-cyclodextrin to build polymer bilayers on negatively charged surfaces, and to investigate the interactions between such layers. The association of this system in solution has been studied by rheology, light scattering, and fluorescence measurements. It was found that the adamantane-terminated PEO (PEC-Ad) mixed with the beta-cyclodextrin polymer gives complexes where the interpolymer links are formed by specific inclusion of the adamantane groups in the beta-cyclodextrin cavities. This results in a higher viscosity of the solution and growth of intermolecular clusters. The interactions between surfaces coated with a cationized beta-cyclodextrin polymer across a water solution containing PEO-Ad polymers were studied by employing the interferometric surface force apparatus (SFA). In the first step, the interaction between mica surfaces coated with the cationized beta-cyclodextrin polymer in pure water was investigated. It was found that the beta-cyclodextrin polymer adsorbs onto mica and almost neutralizes the surface charge. The adsorbed layers of the beta-cyclodextrin polymer are rather compact, with a layer thickness of about 60 Angstrom (30 Angstrom per surface). Upon separation, a very weak attractive force is observed. The beta-cyclodextrin solution was then diluted by pure water by a factor of 3000 and a PEO-Ad polymer was introduced into the solution. Two different architectures of the PEO-Ad polymer were investigated: a four-arm structure and a linear structure. After the adsorption of the PEO polymer onto the beta-cyclodextrin layer reached equilibrium, the forces were measured again. It was found that the weak repulsive long-range force had disappeared and an attractive force caused the surfaces to jump into contact, and that the compressed layer thickness had increased. The attractive force is interpreted as being due to a specific recognition between the hydrophobic adamantane groups on the PEO-Ad polymer and the hydrophobic cavity in the beta-cyclodextrin molecules. Furthermore, the attractive force observed on separation has increased significantly, which is a further indication of a specific interaction between the beta-cyclodextrin polymer and the adamantane groups.

  • 23.
    Blomberg, Eva
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Poptoshev, Evgeni
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Caruso, F.
    Centre for Nanoscience and Nanotechnology, Department of Chemical and Biomolecular Engineering, University of Melbourne, Victoria, Australia.
    Surface interactions during polyelectrolyte multilayer build-up. 2. The effect of ionic strength on the structure of preformed multilayers2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 9, 4153-4157 p.Article in journal (Refereed)
    Abstract [en]

    Interactions between surfaces bearing multilayer films of poly(allylamine hydrochloride) (PAH) and poly(styrenesulfonate sodium salt) (PSS) were investigated across a range of aqueous KBr solutions. Three layer films (PAH/PSS/PAH) were preassembled on mica surfaces, and the resulting interactions were measured with the interferometric surface force apparatus (SFA). Increasing the ionic strength of the medium resulted in a progressive swelling of the multilayer films. Interactions in solutions containing more than 10(-3) M KBr were dominated by a long-ranged steric repulsion originating from compression of polyelectrolyte segments extending into solution. In 10(-1) M KBr, repeated measurements at the same contact position showed a considerable reduction of the range and the strength of the steric force, indicating a flattening of the film during initial approach. Furthermore, this flattening was irreversible on the time scale of the experiments, and measurements performed up to 72 h after the initial compression showed no signs of relaxation. These studies aid in understanding the dominant interactions between polyelectrolyte multilayers, including polyelectrolyte films deposited on colloidal particles, which is important for the preparation of colloidally stable nanoengineered particles.

  • 24.
    Blomberg, Eva
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Verrall, Ronald
    Department of Chemistry, University of Saskatchewan, Saskatoon, Canada.
    Claesson, Per M
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Interactions between adsorbed layers of cationic gemini surfactants2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 4, 1133-1140 p.Article in journal (Refereed)
    Abstract [en]

    The forces acting between glass and between mica surfaces in the presence of two cationic gemini surfactants, 1,4 diDDAB (1,4-butyl-bis(dimethyldodecylammonium bromide)) and 1,12 diDDAB (1,12-dodecyl-bis(dimethyldodecylammonium bromide)), have been investigated below the critical micelle concentration (cmc) of the surfactants using two different surface force techniques. In both cases, it was found that a recharging of the surfaces occurred at a surfactant concentration of about 0.1 x cmc, and at all surfactant concentrations investigated repulsive double-layer forces dominated the interaction at large separations. At smaller separations, attractive forces, or regions of separation with (close to) constant force, were observed. This was interpreted as being due to desorption and rearrangement in the adsorbed layer induced by the proximity of a second surface. Analysis of the decay length of the repulsive double-layer force showed that the majority of the gemini surfactants were fully dissociated. However, the degree of ion pair formation, between a gemini surfactant and a bromide counterion, increased with increasing surfactant concentration and was larger for the gemini surfactant with a shorter spacer length.

  • 25.
    Blute, Irena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pugh, Robert J.
    van de Pas, John
    Callaghan, Ian
    Silica nanoparticle sols 1: Surface chemical characterization and evaluation of the foam generation (foamability)2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 313, no 2, 645-655 p.Article in journal (Refereed)
    Abstract [en]

    Surface characterization and foaming studies were carried out with nine industrially manufactured, colloidal silica dispersions with particles sizes from 5-40 nm. All the silica sols produced transient foams with short decay times and the dynamic foam generation (foamability) was found to vary according to the sol type with the greatest foamability occurring for the hydrophobically modified sol and the deionized hydrophilic sol. However, it was found that improved foamability of all the sols could be achieved by changing the pH to within the region of the pH(pzc) which corresponds to the region of lowest hydrophilicity. An increase in pH (and build-up of negative charge) enhances the surface hydrophilicity and caused a decrease in foamability. In addition, for selected hydrophilic sols, it was shown that the foamability (a) increased with decrease in particle size (within the 6-40 nm range) and (b) increased with particle concentration (within the range of 1-15 wt%). Overall, it was concluded that the foamability was primary controlled by hydrophobicity (and hence by pH) and also by the particle concentration, the particle size and the degree of agglomeration.

  • 26.
    Blute, Irena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pugh, Robert J.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    van de Pas, John
    Callaghan, Ian
    Silica nanoparticle sols. Part 3: Monitoring the state of agglomeration at the air/water interface using the Langmuir-Blodgett technique2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 336, no 2, 584-591 p.Article in journal (Refereed)
    Abstract [en]

    Langmuir-Blodgett films were prepared at the air/water interface from dispersions of hydrophilic and partially, hydrophobically modified industrially manufactured silica nanoparticles. The hydrophilic particles featured expanded, fairly easily compressible, surface pressure (pi)-area (A) isotherms with well defined collapse pressures which appeared to be caused by the formation of loosely structured agglomerates which exhibited elastic behavior at low surface pressure and inelastic behavior at high surface pressure. Lateral electrostatic interparticle interactions seemingly played an important role in this hydrophilic system. This contrasted with the hydrophobically modified particles which were more difficult to disperse in the ethanol/chloroform spreading solvent and appeared to be in the semi-agglomerated state at low surface pressures and exhibited a more difficult to compress compacted film. Both types of particulate films were shown to be sensitive to the spreading environment and changes in pH were found to increase particle agglomeration which drastically reduced the particulate area for the hydrophilic sol but less so, in the case of the moderately hydrophobically modified sol. In general, the LB technique proved to be a useful method to monitor changes in the state of aggregation of narrosized silica particles at the air/water interface. These results also appear to give some support of our ideas, presented in earlier publications [1,2] in which it was suggested that the major role of the hydrophobically modified hydrophilic particles in foaming was to produce an aggregated particulate film surrounding the air/water interface which provides a physical barrier preventing coalescence of bubbles.

  • 27.
    Bodvik, Rasmus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Karlson, Leif
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Temperature-dependent adsorption of cellulose ethers on silica and hydrophobized silica immersed in aqueous polymer solution2011In: RSC ADVANCES, ISSN 2046-2069, Vol. 1, no 2, 305-314 p.Article in journal (Refereed)
    Abstract [en]

    The influence of temperature on adsorption and the adsorbed layer properties of methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC) were investigated on silica and hydrophobized silica surfaces immersed in aqueous polymer solution. To achieve a concise understanding a quartz crystal microbalance with dissipation, ellipsometry, and atomic force microscopy imaging were employed. These techniques provide complimentary information on the structure, mass and viscoelastic properties of the polymer layers. Adsorption was first allowed at 25 degrees C. Next, the temperature was increased step-wise up to 50 degrees C and then decreased again. This procedure highlights the temperature dependence of the adsorbed material, as well as the hysteresis in the adsorption due to temperature cycling. A change in temperature not only affects the adsorbed amount, but also the properties of the layer as illustrated by measurements of its water content, thickness and viscoelasticity.

  • 28. Cardenas, Marite
    et al.
    Valle-Delgado, Juan Jose
    Hamit, Jildiz
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Arnebrant, Thomas
    Interactions of hydroxyapatite surfaces: Conditioning films of human whole saliva2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 14, 7262-7268 p.Article in journal (Refereed)
    Abstract [en]

    Hydroxyapatite is a very interesting material given that it is the main component in tooth enamel and because of its uses in bone implant applications. Therefore, not only the characterization of its surface is of high relevance but also designing reliable methods to study the interfacial properties of films adsorbed onto it. In this paper we apply the colloidal probe atomic force microscopy method to investigate the surface properties of commercially available hydroxyapatite surfaces (both microscopic particles and macroscopic discs) in terms of interfacial and frictional forces. In this way, we find that hydroxyapatite surfaces at physiological relevant conditions are slightly negatively charged. The surfaces were then exposed to human whole saliva, and the surface properties were re-evaluated. A thick film was formed that was very resistant to mechanical stress. The frictional measurements demonstrated that the film was indeed highly lubricating, supporting the argument that this system may prove to be a relevant model for evaluating dental and implant systems.

  • 29.
    Claesson, P. M.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Dedinaite, A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Mészáros, R.
    Varga, I.
    Association between Polyelectrolytes and Oppositely Charged Surfactants in Bulk and at Solid/Liquid Interfaces2010In: Colloids and Interface Science Series, Wiley-Blackwell, 2010, Vol. 3, 337-395 p.Chapter in book (Other academic)
    Abstract [en]

    Mixtures of polyelectrolytes and oppositely charged surfactants find applications in many processes and products that are used in our daily life. Such systems also show many interesting features from a scientific point of view. Due to the combined technological relevance and scientific challenge, considerable research efforts have been made in this area in recent years. This has resulted in new theoretical approaches, the development of simulation methods and new experimental techniques and, of course, a large body of new findings. Together, these efforts have increased the understanding significantly, especially during the last 5 years. This chapter reviews some aspects of this topic, focusing on bulk association and association at solid/liquid interfaces. The review is focused on developments during the 21st century, even though in some cases a historical perspective is also offered.

  • 30.
    Claesson, Per M.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Kjellin, Mikael
    Rojas, Orlando J.
    Stubenrauch, Cosima
    Short-range interactions between non-ionic surfactant layers2006In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 8, no 47, 5501-5514 p.Article, review/survey (Refereed)
    Abstract [en]

    Short-range interactions between surfactant and lipid layers are of great importance in technical applications in complex fluids such as foams, dispersions and emulsions, as well as in the formulation and performance of dispersants, detergents and flocculants. It is also of utmost importance in biological systems where interactions between biomembranes influence a range of processes. The field of short-range interactions has been thoroughly investigated during the past 30 years, following the emergence of a number of techniques to measure interaction forces, Thus, our understanding has increased considerably and it is timely to summarize relevant knowledge accumulated in this area. In this review we focus on the nature of short-range interactions between non-ionic and zwitterionic surfactant and lipid layers exposing their polar groups to the surrounding medium. We discuss the complex interplay of short-range (van der Waals, hydration, steric and other) forces based on recent theoretical and experimental results.

  • 31.
    Claesson, Per M.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Naderi, A.
    Iruthayaraj, J.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Vareikis, A.
    Makuska, R.
    Interfacial properties of bottle-brush polyelectrolytes2007In: PROCEEDINGS OF BALTIC POLYMER SYMPOSIUM 2007 / [ed] Makuska, R., Vilnius: VILNIUS UNIV. , 2007, 77-81 p.Conference paper (Refereed)
    Abstract [en]

    This article is focused on interfacial properties of bottle brush polyelectrolytes, where side-chains are attached along a polymer backbone. This class of polymer has been much less studied than block copolymers, which is particularly true for bottle brush polyelectrolytes with a high graft density. We have explored how the graft density and charge density of such polymers affect surface properties, as well as some bulk properties. The adsorption of this class of polymer onto negatively charged silica and mica surfaces has been determined. On mica adsorption is driven by electrostatic forces whereas on silica both electrostatic forces and interactions between silica and ethylene oxide chains drive the adsorption. On silica the adsorbed amount is very sensitive to solution ionic strength and pH. We also report on surface interactions and frictional forces obtained between surfaces coated with bottle brush polyelectrolytes.

  • 32.
    Claesson, Per M.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Poptoshev, Evgeni
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Dedinaite, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Polyelectrolyte-mediated surface interactions2005In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 114, 173-187 p.Article, review/survey (Refereed)
    Abstract [en]

    The current understanding of interactions between surfaces coated with polyelectrolytes is reviewed. Experimental data obtained with various surface force techniques are reported and compared with theoretical predictions. The majority of the studies concerned with interactions between polyelectrolyte-coated surfaces deal with polyelectrolytes adsorbed to oppositely charged surfaces, and this is also the main focus of this review. However, we also consider polyelectrolytes adsorbed to uncharged surfaces and to similarly charged surfaces, areas where theoretical predictions are available, but relevant experimental data are mostly lacking. We also devote sections to interactions between polyelectrolyte brush-layers and to interactions due to non-adsorbing polyelectrolytes. Here, a sufficient amount of both theoretical and experimental studies are reported to allow us to comment on the agreement between theory and experiments. A topic of particular interest is the presence of trapped non-equilibrium states that often is encountered in experiments, but difficult to treat theoretically.

  • 33.
    Dedinaite, Andra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Bastardo Zambrano, Luis Alejandro
    Oliveira, C. P.
    Pedersen, J. S.
    Claesson, Per M
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Vareikis, A.
    Makuska, R.
    Solution properties of bottle-brush polyelectrolytes2007In: PROCEEDINGS OF BALTIC POLYMER SYMPOSIUM 2007    , 2007, 112-116 p.Conference paper (Refereed)
    Abstract [en]

    Aqueous solution properties of bottle brush polyelectrolytes, where side-chains are attached to a polymer backbone, have been studied. The side chains consist of 45 units long poly(ethylene oxide) groups and the backbone is of the methacrylate type. Small-angle X-ray scattering (SAXS) was used to elucidate the solution conformation of this class of polymer and how it is affected by the side chain density and charge density. The effect of temperature on the solution conformation, and in particular the side chain extension, has also been quantified. At higher concentrations the interactions between the polymer chains in solution affects the scattering, and it is shown that this interaction is well described by a model originally developed for wormlike micelles.

  • 34.
    Dedinaite, Andra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Mohanty, Biswaranjan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Claesson, Per M
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Lubrication by organized soft matter2010In: SOFT MATTER, ISSN 1744-683X, Vol. 6, no 7, 1520-1526 p.Article in journal (Refereed)
    Abstract [en]

    The AFM-colloidal probe technique has been used to explore surface interactions and friction forces between polyelectrolyte-coated surfaces immersed in aqueous solutions in the absence and presence of surfactant. It is found that the nature of the load bearing forces is decisive for the lubricating properties of the layers. Low frictional forces are obtained when the load is carried by a force that allows the interfacial layer to have a high fluidity, whereas attractive surface forces most often increase the friction. Highly charged polyelectrolytes and oppositely charged surfactants associate in bulk solution to form complexes with a well-defined internal structure. At the surface, similarly structured polyelectrolyte-surfactant layers are spontaneously formed. Such layers have a high load bearing capacity, and the friction coefficient is very low as long as the integrity of the layer remains intact. Interestingly, when the load is increased step-wise the friction force as a function of load displays some sharp peaks, which are identified as being due to structural rearrangements in the polyelectrolyte-surfactant layer. On unloading very low frictional forces are obtained despite the presence of an adhesion between the layers. To maintain the favorable lubricating properties it is essential to have surfactants present in solution, whereas, after the initial adsorption step, there is no need to have the polyelectrolyte present in the bulk. The reason for this is the essentially irreversible adsorption of the polyelectrolyte.

  • 35.
    Deguchi, Shigeru
    et al.
    Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, Yokosuka 237-0061, Japan.
    Shimoshige, Hirokazu
    Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, Yokosuka 237-0061, Japan.
    Tsudome, Mikiko
    Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, Yokosuka 237-0061, Japan.
    Mukai, Sada-atsu
    Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, Yokosuka 237-0061, Japan.
    Corkery, Robert W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Ito, Susumu
    Department of Bioscience and Biotechnology, Faculty of Agriculture, University of the Ryukyus, Nishihra, Okinawa 903-0213, Japan.
    Horikoshi, Koki
    Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, Yokosuka 237-0061, Japan.
    Microbial growth at hyperaccelerations up to 403,627 x g2011In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 108, no 19, 7997-8002 p.Article in journal (Refereed)
    Abstract [en]

    It is well known that prokaryotic life can withstand extremes of temperature, pH, pressure, and radiation. Little is known about the proliferation of prokaryotic life under conditions of hyperacceleration attributable to extreme gravity, however. We found that living organisms can be surprisingly proliferative during hyperacceleration. In tests reported here, a variety of microorganisms, including Gram-negative Escherichia coli, Paracoccus denitrificans, and Shewanella amazonensis; Gram-positive Lactobacillus delbrueckii; and eukaryotic Saccharomyces cerevisiae, were cultured while being subjected to hyperaccelerative conditions. We observed and quantified robust cellular growth in these cultures across a wide range of hyperacceleration values. Most notably, the organisms P. denitrificans and E. coli were able to proliferate even at 403,627 × g. Analysis shows that the small size of prokaryotic cells is essential for their proliferation under conditions of hyperacceleration. Our results indicate that microorganisms cannot only survive during hyperacceleration but can display such robust proliferative behavior that the habitability of extraterrestrial environments must not be limited by gravity.

  • 36.
    Dédinaité, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Monolayer Properties Probed by Surface Forces Measurements2007In: Advanced chemistry of monolayers at interfaces: trends in methodology and technology, Elsevier, 2007, 23-53 p.Chapter in book (Refereed)
    Abstract [en]

    In a review like this it is impossible to refer to even a small fraction of all the interesting work that has been done with the SFA. Anyway, I hope to have illustrated some selected areas in which the SFA has played a major role for increasing our understanding. It is fascinating to see how the development of the "basic SFA" is continued in many laboratories. One clear focus of modern developments is towards studies of dynamic phenomena, another is to combine the SFA with spectroscopy in order to gain further molecular understanding of matter in confinement. The coming years will be exciting and promise new developments that will allow us to develop our understanding of colloids, biophysical systems and complex liquids at and between interfaces.

  • 37.
    Dédinaité, Andra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Iruthayaraj, Joseph
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Gorochovceva, Natalija
    Department of Polymer Chemistry, Vilnius University.
    Makuška, Ričardas
    Department of Polymer Chemistry, Vilnius University.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Interfacial Properties of Chitosan-PEO graft Oligomers: Surface Competition with Unmodified Chitosan Oligomers2006In: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 132, 124-130 p.Article in journal (Refereed)
    Abstract [en]

    Oligomers of chitosan carrying 45 units long poly(ethylene oxide), PEO, chains grafted to the C-6 position of the sugar units were prepared using a novel synthesis route. The graft density was high, close to one poly(ethylene oxide) chain grafted to each sugar unit of the chitosan oligomer but a small fraction of unreacted chitosan remained in the sample. The molecular weight distribution of the sample was determined using GPC. The interfacial properties of the chitosan-PEO graft oligomers were evaluated using X-ray photoelectron spectroscopy and surface force measurements. It was found that the small fraction of unreacted chitosan was significantly enriched at the solid-solution interface on negatively charged muscovite mica surfaces. The interactions between chitosan-PEO oligomer coated surfaces were found to be dominated by the extended PEO chains, and at high coverage the measured forces were consistent with those expected for polymer brushes. Addition of salt up to 10 mM did not result in any significant desorption of preadsorbed oligomer layers.

  • 38.
    Ekholm, P.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Claesson, Per M
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Auflem, I. H.
    Department of Chemical Engineering, The Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
    Sjöblom, J.
    Department of Chemical Engineering, The Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
    Kornfeldt, A.
    ABB Corporate Research, Västerås, Sweden.
    A quartz crystal microbalance study of the adsorption of asphaltenes and resins onto a hydrophilic surface2002In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 247, no 2, 342-350 p.Article in journal (Refereed)
    Abstract [en]

    The adsorption of extracted and purified samples of asphaltenes and resins onto gold surfaces has been studied as a function of bulk concentration using a quarts crystal microbalance with dissipation measurements (QCM-D). With this device, which works equally well in transparent, opaque, and nontransparent samples, the adsorbed amount is measured through a change in resonant frequency of the quartz oscillator. The measured change in dissipation reports on changes in layer viscoelasticity and slip of the solvent at the surface. The results show that the adsorbed amount for resins from heptane corresponds to a rigidly attached monolayer. The adsorbed amount decreases with increasing amount of toluene in the solvent and is virtually zero in pure toluene. Asphaltenes, on the other hand, adsorb in large quantities and the mass and dissipation data demonstrate the presence of aggregates on the surface. The aggregates are firmly attached and cannot be removed by addition of resins. On the other hand, resins and asphaltenes associate in bulk liquid and the adsorption from mixtures containing both resins and asphaltenes is markedly different from that obtained from the pure components. Hence, we conclude that preformed resin aggregates adsorb to the surface. These results are compared and discussed in relation to adsorption from crude oil diluted in heptane/toluene mixtures.

  • 39. Feiler, A. A.
    et al.
    Jenkins, P.
    Rutland, Mark W
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Effect of relative humidity on adhesion and frictional properties of micro- and nano-scopic contacts2005In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 19, no 05-mar, 165-179 p.Article in journal (Refereed)
    Abstract [en]

    The effect of relative humidity (RH) oil the interactions of AFM tips and colloidal probes with hydrophilic silica substrates is investigated. Both friction and adhesion are studied. For the case of a colloidal probe the interaction is characteristic of a multiasperity contact, the adhesion increased with increasing RH and above a certain threshold relative humidity a large increase in adhesion was measured. This behaviour is explained in terms of a recent model where the Kelvin radius of the condensate becomes larger than some characteristic roughness on the surface. The interaction between the tip and the substrate also exhibited an increase in adhesion above a threshold RH although the increase was much less marked than with the colloid probe. The friction decreased with increasing humidity for both tip and colloid probe although the friction force was much less sensitive than adhesion to changes in RH. Stick-slip behaviour was observed between tip and substrate for all humidities at high loads, but only at the lowest RH (about 5%) it was observed at all loads. At higher humidity the behaviour became increasingly continuum on the experimental timescale, presumably due to viscous contributions from the water. Stick-slip was not observed for the colloidal probe friction measurements.

  • 40. Feiler, Adam A.
    et al.
    Bergstrom, Lennart
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Superlubricity using repulsive van der Waals forces2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 6, 2274-2276 p.Article in journal (Refereed)
    Abstract [en]

    Using colloid probe atomic force microscopy, we show that if repulsive van der Waals forces exist between two surfaces prior to their contact then friction is essentially precluded and supersliding is achieved. The friction measurements presented here are of the same order as the lowest ever recorded friction coefficients in liquid, though they are achieved by a completely different approach. A gold sphere attached to an AFM cantilever is forced to interact with a smooth Teflon surface (templated on mica). In cyclohexane, a repulsive van der Waals force is observed that diverges at short separations. The friction coefficient associated with this system is on the order of 0.0003. When the refractive index of the liquid is changed, the force can be tuned from repulsive to attractive and adhesive. The friction coefficient increases as the Hamaker constant becomes more positive and the divergent repulsive force, which prevents solid-solid contact, gets switched off.

  • 41.
    Feiler, Adam A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Jenkins, Paul
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Effect of relative humidity on adhesion and frictional properties of micro- and nano-scopic contacts2005In: Atomic Force Microscopy in Adhesion Studies, Leiden-Boston: VSP , 2005, 491-505 p.Chapter in book (Refereed)
  • 42.
    Feiler, Adam
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Stiernstedt, Johanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Theander, Katarina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Jenkins, Paul
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Effect of capillary condensation on friction force and adhesion2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 2, 517-522 p.Article in journal (Refereed)
    Abstract [en]

    Friction force measurements have been conducted with a colloid probe on mica and silica (both hydrophilic and hydrophobized) after long (24 h) exposure to high-humidity air. Adhesion and friction measurements have also been performed on cellulose substrates. The long exposure to high humidity led to a large hysteresis between loading and unloading in the friction measurements with separation occurring at large negative applied loads. The large hysteresis in the friction - load relationship is attributed to a contact area hysteresis of the capillary condensate which built up during loading and did not evaporate during the unloading regime. The magnitude of the friction force varied dramatically between substrates and was lowest on the mica substrate and highest on the hydrophilic silica substrate, with the hydrophobized silica and cellulose being intermediate. The adhesion due to capillary forces on cellulose was small compared to that on the other substrates, due to the greater roughness of these surfaces.

  • 43.
    Feldötö, Zsombor
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Dédinaité, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Mucin-electrolyte interactions at the solid-liquid interface probed by QCM-D2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 7, 3348-3357 p.Article in journal (Refereed)
    Abstract [en]

    The interaction between mucin and ions has been investigated by employing the quartz crystal microbalance technique with measurement of energy dissipation. The study was partially aimed at understanding the adsorption of mucin on surfaces with different chemistry, and for this purpose, surfaces exposing COOH, OH, and CH3 groups were prepared. Mucin adsorbed to all three types of functionalized gold surfaces. Adsorption to the hydrophobic surface and to the charged hydrophilic surface (COOH) occured with high affinity despite the fact that in the latter case both mucin and the surface were negatively charged. On the uncharged hydrophilic surface exposing OH groups, the adsorption of mucin was very low. Another aim was to elucidate conformational changes induced by electrolytes on mucin layers adsorbed on hydrophobic surfaces from 30 mM NaNO3. To this end, we investigated the effect of three electrolytes with increasing cation valance: NaCl, CaCl2, and LaCl3. At low NaCl concentrations, the preadsorbed layer expands, whereas at higher concentrations of NaCl the layer becomes more compact. This swelling/compacting of the mucin layer is fully reversible for NaCl. When the mucin layer instead is exposed to CaCl2 or LaCl3, compaction is observed at I mM. For CaCl2, this process is only partially reversible, and for LaCl3, the changes are irreversible within the time frame of the experiment. Finally, mucin interaction with the DTAB cationic surfactant in an aqueous solution of different electrolytes was evaluated with turbidimetry measurements. It is concluded that the electrolytes used in this work screen the association between mucin and DTAB and that the effect increases with increasing cation valency.

  • 44. Gilanyi, Tibor
    et al.
    Varga, Imre
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Stubenrauch, Cosima
    Meszaros, Robert
    Adsorption of alkyl trimethylammonium bromides at the air/water interface2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 317, no 2, 395-401 p.Article in journal (Refereed)
    Abstract [en]

    A number of features of the adsorption of alkyl trimethylammonium bromides with n(c) = 10, 12, 14, and 16 at the air/water interface were studied. First, the adsorption isotherms were calculated front experimental surface tension vs concentration curves by means of the Gibbs equation. Second, a novel method was used to estimate the adsorption free energy change. From the analysis of these data it was concluded that the hydrophobic driving force for the adsorption first increases with increasing adsorbed amount and then levels off in a plateau, which holds true for all four homologues. This peculiar behavior was interpreted by the formation of a thin liquid-like alkane film at the air/water interface once a certain adsorbed amount is exceeded. The hydrophobic contribution to the standard free energy change of adsorption was compared with those values previously determined for alkyl sulfate homologues. This comparison suggests that the alkyl trimethylammonium type surfactants behave as if their alkyl chain was approximately one methylene group shorter than those of the corresponding alkyl sulfates.

  • 45. Gorochovceva, N.
    et al.
    Naderi, A.
    Dedinaite, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Makuska, R.
    Chitosan-N-poly(ethylene glycol) brush copolymers: Synthesis and adsorption on silica surface2005In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 41, no 11, 2653-2662 p.Article in journal (Refereed)
    Abstract [en]

    Chitosan-N-poly(ethylene glycol) brush copolymers with different degree of substitution (DS) were synthesized via reductive amination of chitosan by rnethoxy poly(ethylene glycol) (MPEG) aldehyde. Chitosan-N-MPEG copolymers were high-molecular-weight products with desirable DS; solubility and solution viscosity of those copolymers depended on the method of the synthesis of MPEG aldehyde and on DS. Synthesis of MPEG aldehyde by the use of TEMPO radical/BAIB was not suitable because of partial oxidation of methoxy groups of MPEG resulting in bifunctional PEG derivatives leading to cross-linking. Adsorption studies of chitosan-N-MPEG graft copolymers oil silica surface show that these polymers adsorb in highly hydrated layers.

  • 46.
    Halthur, Tobias
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Multilayer Structures for Biomaterial Applications: Biomacromolecule-based Coatings2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The cellular response to a biomaterial, such as a dental implant, is mainly governed by the surface properties, and can thus be altered by the introduction of a surface coating. In this thesis the buildup of a biomacromolecule-based coating formed by layerby-layer (LbL) deposition of the charged polypeptides poly(L-lysine) (PLL) and poly(L-glutamic acid) (PGA) has been studied. In an attempt to make these coatings bioactive and useful for bone-anchored implants, an amelogenin protein mixture (EMD), has been immobilized in these thin polyelectrolyte multilayer (PEM) films. Multilayers were also built by LbL deposition of the natural biomacromolecules collagen (Col) and hyaluronic acid (HA). Multilayer films of these two extra-cellular biomacromolecules should be of interest for use as a scaffold for tissue engineering.

    The buildup of the multilayer films has been followed in situ, using ellipsometry, quartz crystal microbalance with dissipation (QCM-D), and dual polarization interferometry (DPI). The studied PLL/PGA multilayers were found to be highly hydrated, and to exhibit a two-regime buildup behavior, with an initial “slow-growing” regime, and a second “fast-growing” regime with a linear growth in film thickness and more than linear growth in mass. A net diffusion of polypeptides into the film during the buildup led to an increase in density of the films for each layer adsorbed. A change in density was also observed in the Col/HA film, where HA penetrated and diffused into the porous fibrous Col network.

    The formed PLL/PGA films were further found to be rather stable during drying, and post-buildup changes in temperature and pH, not losing any mass as long as the temperature was not raised too rapidly. The film thickness responded to changes in the ambient media and collapsed reversibly when dried. A swelling/de-swelling behavior of the film was also observed for changes in the temperature and pH.

    The EMD protein adsorbed to silica surfaces as nanospheres, and could by itself form multilayers. The adsorption of EMD onto PLL/PGA multilayer films increased at lower pH (5.0), and EMD could be immobilized in several layers by alternate deposition of EMD and PGA.

  • 47.
    Halthur, Tobias
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Björklund, Anna
    YKI, Institute for Surface Chemistry.
    Elofsson, Ulla
    YKI, Institute for Surface Chemistry.
    Self-assembly/aggregation behavior and adsorption of enamel matrix derivate protein to silica surfaces2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 5, 2227-2234 p.Article in journal (Refereed)
    Abstract [en]

    Adsorption of the amelogein protein mixture enamel matrix derivate (EMD) to silica surfaces has been studied by in situ ellipsometry and quartz crystal microbalance with dissipation (QCM-D). The protein was found to adsorb as nanospheres in mono- or multilayers, depending on the concentration of "free" nanospheres available in solution. The concentration of free nanospheres is determined by the competitive processes of adsorption and rapid aggregation into microscopic particles, measured by dynamic light scattering (DLS). Multilayers could also be formed by sequential injections of fresh EMD solution. At higher temperature, an up to 6 times thicker gel-like film was formed on the substrate surface, and decreasing the pH lead to disruption of the multi layer/aggregate formation and a decreased amount adsorbed.

  • 48.
    Halthur, Tobias
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Elofsson, Ulla
    Immobilization of Enamel Matrix Derivate Protein onto Polypeptide Multilayers: Comparative in Situ Measurements using Ellipsometry, Quartz Crystal Microbalance with Dissipation, and Dual Polarization Interferometry2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 26, 11065-11071 p.Article in journal (Refereed)
    Abstract [en]

    The buildup of biodegradable poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and titanium surfaces and the immobilization of enamel matrix derivate (EMD) protein was followed by utilizing in situ ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry (DPI). The use of the relatively new DPI technique validated earlier published ellipsometry measurements of the PLL-PGA polypeptide films. The hydrophobic aggregating EMD protein was successfully immobilized both on top of and within the multilayer structures at pH 5.0. DPI measurements further indicated that the immobilization of EMD is influenced by the flow pattern during adsorption. The formed polypeptide-EMD multilayer films are of interest since it is known that EMD is able to trigger cell response and induce biomineralization. The multilayer films thus have potential to be useful as bioactive and biodegradable coatings for future dental implants.

  • 49.
    Hull, Angelica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Golubkov, I.
    Kronberg, B.
    Van Stam, J.
    Alternative fuel for a standard diesel engine2006In: International Journal of Engine Research, ISSN 1468-0874, E-ISSN 2041-3149, Vol. 7, no 1, 51-63 p.Article in journal (Refereed)
    Abstract [en]

    Alternative fuels have been developed for the commercial diesel products Mkl and EN590. Appropriate additives were selected from a broad range of oxygenates including alcohols, acetals, ethers, esters, and nitrates by a process of systematic elimination. The resulting fuels called Biodiesel 15 meet all existing standards in force for diesel fuel, are stable, and have similar performance characteristics to standard diesel. Significantly Biodiesel 15 is much cleaner than standard diesel with around 30 per cent or more reductions in particulate matter in the exhaust emissions. Carbon dioxide (CO2) emissions are much lower with Biodiesel 15 than with standard diesel products. Other regulated emissions are on a par with Mkl. The fuel consumption of Biodiesel 15 is 2 per cent lower than that of conventional Mkl.

  • 50.
    Iruthayaraj, Joseph
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Poly(Ethylene Oxide) Based Bottle-Brush Polymers and their Interaction with the Anionic Surfactant Sodium Dodecyl Sulphate: Solution and Interfacial Properties2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The aim of this thesis work is to study the physico-chemical properties of poly(ethylene oxide), PEO, based brush polymers both in solution and at solid/aqueous interfaces. The importance of studying the surface properties of brush polymers can be related to a broad spectrum of interfacial-related applications such as colloidal stability, lubrication, detergency, protein repellency to name a few. In many applications it is desirable to form brush-like structures through simple physisorption. In this context the surface properties of PEO based brush polymers differing in molecular architecture were studied, using ellipsometry and surface force apparatus (SFA), to gain some understanding regarding the effect of molecular architecture on the formation of brush structures. The molecular architecture was varied by varying the charge/PEO ratio along the backbone. This study demonstrates that the formation of a brush structure at solid/aqueous interface is due to interplay between the attraction of the backbone to the surface and the repulsions between the PEO side chains. An optimal balance between the two antagonistic factors is required if one aims to build a well-defined brush structure at the interface. In this study the brush-like structures are formed when 25-50% of the backbone segments carry poly(ethylene oxide) side chains. Scattering techniques such as light and neutron reveal that these brush polymers are stiff-rods up to a charge to PEO ratio of 75:25. These stiff PEO brush polymer easily replace the more flexible linear PEO at the silica/water interface, the reason being that the entropy loss on adsorption is smaller for the brush polymer due to its stiff nature.  Polymer-surfactant systems play a ubiquitous role in many technical formulations. It is well known that linear PEO, which adopts random coil conformation in aqueous solution, interact strongly with the anionic surfactant, Sodium Dodecyl Sulphate (SDS). It is of interest to study the interaction between SDS and brush PEO owing to the fact that the PEO side chains have limited flexibility as compared to the linear PEO.  The interaction between brush PEO and the anionic surfactant SDS in solution are studied using different techniques such as NMR, tensiometry, SANS and light scattering. The main finding of this study is that the interaction is weaker compared to the linear PEO-SDS interactions which poses an interesting question regarding the role of chain flexibility in polymer-surfactant interactions.

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